A very simple and rapid spectrophotometric method using measurements at zero-crossing wavelength is described for resolving binary mixtures of riboflavine (E-101) and sunset yellow (E-110) in a powder drink. The assay procedure for E-110 and E-101 involves the extraction of the colorants from the powder drink with pH 4.5 acetate buffer, filtration, appropriate dilution, and measurement of the first derivative absorbance values (denoted as 1D). Calibration graphs are linear up to 25.0 m g.mL-1 for E-101 and 40.0 m g.mL-1 for E-110. The sensitivity and reproducibility of the method were determined by using the synthetic mixtures in different ratios prepared by us, and the proposed method was applied to a commercially available powder drink. The relative standard deviations obtained are 1.39% and 1.15% and the average percentage recoveries are 101.0% and 102.8% for E-101 and E-110, respectively.

A very simple and rapid spectrophotometric method using measurements at zero-crossing wavelength is described for resolving binary mixtures of riboflavine (E-101) and sunset yellow (E-110) in a powder drink. The assay procedure for E-110 and E-101 involves the extraction of the colorants from the powder drink with pH 4.5 acetate buffer, filtration, appropriate dilution, and measurement of the first derivative absorbance values (denoted as 1D). Calibration graphs are linear up to 25.0 m g.mL-1 for E-101 and 40.0 m g.mL-1 for E-110. The sensitivity and reproducibility of the method were determined by using the synthetic mixtures in different ratios prepared by us, and the proposed method was applied to a commercially available powder drink. The relative standard deviations obtained are 1.39% and 1.15% and the average percentage recoveries are 101.0% and 102.8% for E-101 and E-110, respectively.